1. Field of the Invention
The present invention relates in general to electronic circuits and in particular to circuitry for out-of-calibration circuits and methods and systems using the same.
2. Description of the Related Art
In many voltage controlled circuits, precise voltage calibration of the control signals is critical to optimizing performance. For example, in the case of a phase-locked loop (PLL), the voltage controlled oscillator tuning voltage must be set within calibration limits to insure that the proper PLL output frequency is maintained. The calibrated voltage must then be maintained within those limits throughout circuit operation, notwithstanding the tendency of the signal to drift from the calibrated voltage due to temperature rise and/or fluctuations in the supply voltage.
In order to adjust or compensate for voltage changes in a given signal, some technique is required for monitoring that signal and detecting instances when the signal voltage drifts outside the selected calibration tolerance range. Optimally, this technique should be flexible such that it may be used in various applications calling for different nominal calibration voltages and tolerance ranges. Moreover, such a technique should allow for the calibration tolerances to be easily changed, even on the fly, as allowed by the given operating conditions of the device.